In pipe arrangements in a chemical plant and those for fuel gases, water supply, and other purposes, it is necessary to inspect the state of the interior of pipes regularly or at an arbitrary point of time to check, for example, whether or not dirt has adhered to the inner surface of each of the pipes and whether or not the pipes have cracked from the viewpoints of safety, quality control, and other points.
PTL 1 and NPTL 1 describe examples of an apparatus for inspecting the inner surface of a pipe while moving through the pipe.